This is an old artillery game that just got ported to the iPhone and iPod touch. BattleDuel started 1995 on the Amiga computer, a Java version followed 2006 and now it's available for iPhone, iPod and iPad. It features a lot of game modes (tournament, conquer) and options that are not available elsewhere (e.g. team mode). Here is more info on this new iPhone game:

BattleDuel is an artillery game.

Two players fight against each other with cannons placed in a windy mountainous landscape.

To hit the opponent they change the angle, powder, position and weapon of their cannon. A duel is finished if the opponent's cannon is completely destroyed.

BattleDuel features four game modes: duel-mode, two tournament modes and a conquer mode. Computer opponents with three different skill levels provide enough resistance for single players.

The game contains four different landscape types. A large number of configuration and game play options are available that help you to maximize the gaming experience.